Systems for sensing tire conditions and displaying sensed tire condition information to a vehicle occupant are known. Often, such systems are known as tire pressure monitoring systems even though the system may not only sense tire pressure but may also sense other tire conditions such as tire temperature. Such tire pressure monitor systems include a tire-based sensor assembly that senses both the pressure and temperature inside its associated tire and transmits the sensed pressure and temperature information to a vehicle-based receiver, i.e., a receiver mounted in the vehicle. The transmitted sensed tire condition signal may be a coded radio frequency (“RF”) signal. The vehicle-based receiver is connected to a display located in the vehicle cabin to display, for example, a warning signal to the vehicle operator when an under-inflated tire pressure condition exists or an over-heated tire condition occurs.
Each tire-based sensor assembly may have a unique identification code associate therewith. The tire-based sensor assembly transmits a signal that includes the unique identification code and the sensed tire condition. The vehicle-based receiver must associate the received signal from the tire-based sensor assembly, and, in particular, the unique tire identification code, with a particular tire position location on the vehicle so as to display the sensed tire condition information appropriately to the vehicle operator, i.e., display tire pressure/temperature condition and location information so the vehicle operator can identify which tire has a sensed, improper condition.
Associating tire location with tire transmitter unique codes requires a learning process by the vehicle-based receiver. Many processes have been proposed to accomplish this learning function including signal interrogation methods in which each tire-based sensor assembly is separately interrogated. In response to receiving an interrogation signal, the tire-based sensor assembly transmits a response signal having its unique identification information. Upon receipt of the response signal, the vehicle-based receiver associates that unique tire identification code with that tire location since the system “knows” which tire location was just interrogated. The vehicle-based system stores identification codes and tire location correlations in memory for use in its display operation.
U.S. Patent Application Publication US 2006/0142911 of Allard et al. discloses a method and apparatus for locating the position of a wheel on the right or left of a vehicle using signals from two magnetic sensors. U.S. Patent Application Publication US 2006/0044125 of Pierbon discloses a method and apparatus for detecting the right/left position of a wheel on a vehicle using acceleration signals from first and second means capable of measuring acceleration, such as shock sensors incorporating elements made of piezoelectric ceramic. U.S. Patent Application Publication US 2009/0204361 of Watasue discloses a tire rotation detection system and method using an accelerometer and accounting for acceleration due to earth's gravity.